As a procedure for ionizing a sample component in a mass spectrometer, an atmospheric pressure ionization method (ambient ionization method) for ionizing the sample component in an atmospheric atmosphere has been known. The atmospheric pressure ionization method is a technology that enables in situ mass spectrometry in real time without performing special preparation and pretreatment of a sample. Hitherto, a large number of atmospheric pressure ionization technologies using gases called a rare gas and an inert gas excited with discharge plasma have been developed.
Typical related art documents thereof include:
(1) a direct analysis in real time (DART) method (see, for example, Patent Literature 1 and Non Patent Literature 1);
(2) an atmospheric-pressure solids analysis probe (ASAP) method (see, for example, Patent Literature 2 and Non Patent Literature 2);
(3) a desorption corona beam ionization (DCBI) method (see, for example, Patent Literature 3 and Non Patent Literature 3); and
(4) a flowing atmospheric pressure afterglow (FAPA) method (see, for example, Non Patent Literature 4).
In each of the DART, the DCBI, and the FAPA, a helium gas and glow discharge are combined, and in the ASAP, a nitrogen gas and corona discharge are combined.